A 100KB limit is a “nice” constraint: strict enough to improve loading speed and pass most upload portals, but flexible enough that you can keep photos looking natural. The trick is to avoid over-compressing while still staying under the number. This guide shows a repeatable, online-friendly workflow that works for photos, documents, and simple graphics.

What “100KB” actually means (and why you should aim for 95KB)

Some websites treat 100KB as 100,000 bytes, others as 102,400 bytes. To avoid rejection, target a little below the limit—around 90–98KB—so minor metadata differences or platform re-encoding don’t push you over.

Best format choices for 100KB

JPEG: best for photographs and camera images.
PNG: best for logos, UI, flat colors, or when transparency is required.
WebP: often smaller than JPEG at similar visual quality; great for web use when accepted.

Step-by-step: compress an image to ~100KB

Resize first. If the image is huge (e.g., 4000px), reduce the long edge to what you actually need (commonly 1200–2000px for web).
Pick the format. Photos → JPEG/WebP. Logos with transparency → PNG/WebP lossless.
Adjust quality gradually. Start around 85 for JPEG/WebP, then decrease in small steps until you’re just under 100KB.
Strip metadata if available. It saves a few KB and removes location/device details.
Preview at real size. Judge clarity at the display size (not zoomed in).

Recommended settings (practical starting points)

There’s no single perfect quality number, but these are good first tries:

Portrait photo (1200–1600px): JPEG/WebP quality 75–85.
Landscape photo (1600–2000px): JPEG/WebP quality 70–82.
Document photo (text-heavy): consider higher quality (80–88) + smaller dimensions, or convert to a clean scan workflow if readability matters most.

How to keep images sharp under 100KB

Crop dead space before compressing.
Avoid re-encoding multiple times; start from the cleanest original.
Don’t over-sharpen; it amplifies compression artifacts.
Prefer resizing over extreme quality drops when you’re close to the limit.

If it still won’t reach 100KB

If you’re stuck well above 100KB, the image is likely oversized or in the wrong format. Reduce dimensions, switch PNG → JPEG for photos (if transparency isn’t required), and aim for a simpler frame (crop backgrounds). For brand assets with transparency, WebP lossless can sometimes beat PNG at similar fidelity.

The easiest way to stay consistent is to use the same “target width + format + quality range” for each content type in your workflow. Once you find settings that regularly land below 100KB with good quality, you can reuse them for every upload.